Referring initially to FIG. 1, chains 100 have historically been used in dragline buckets 102 in the hoist and drag circuits. Some rigging configurations also use chains in the dump circuit (single dump block systems). Chains 100 have in the past been cast, forged, comprised structural plate, etc.
Looking now at FIG. 2, an example of a dragline bucket chain 100, which is cast as one assembly is shown. The drawbacks to this design include the amount of time it takes to cast the chain, the obstacles with pouring the chain and avoiding casting defects, heat treating the entire length of the chain as well as the space needed to quench the chain, and the time to model the chain assembly. In particular, the length of the apparatus used in heat treating the chain may be undesirably long and expensive to construct as well as take up valuable space. As can be seen, a typical chain 100 includes two end links 104 and a plurality of intermediate or body links 106, all of which are intertwined or interlocked to form the chain. The addition or subtraction of the intermediate or body links makes the chain longer or shorter as desired.
A previous solution to these problems has been to cast the individual links 108 with weld-in sections 110 used on every other link as shown in FIGS. 3 and 4. In practice, the weld-in sections are integrally cast with thinned portions connecting them to the main link member 112. They are then pressed out so that the main link 112 member may be joined to adjacent fully cast links 106 on either side. Then, the weld-in section 110 is replaced and adhered to the main link member 112 using a welding process. As best seen in FIG. 4, grooves 114 are provided into which the welded material is placed to create a welded seam. However, welding in the sections of the chain is time consuming and labor intensive. Furthermore, the selection of the proper weld electrode is critical and any mistakes may lead to undesirable scrap. Also, the welded seams need to withstand the abrasion associated with surface mines and may not be suitably durable over time.
Accordingly, it is desirable to develop a better method for manufacturing chain links than has yet been devised.